The present invention relates to vehicle wheel balancer systems, and in particular, to a vehicle wheel balancer system configured to provide a projected display of information onto a surface of vehicle wheel rim to facilitate completion of a wheel imbalance measurement or correction procedure.
When balancing a vehicle wheel rim and tire assembly, which may consist of either a wheel rim by itself, or a wheel rim on which a tire has been mounted, several potential sources for operator error exist. First, there is a need to identify the proper correction planes on the wheel rim at which imbalance correction weights are to be placed. Second, the wheel rim and tire assembly must be correctly rotated to, and held in, a rotational position such that the operator can place an imbalance correction weight in the identified correction plane, and third, the operator must manually apply the imbalance correction weight to the wheel rim in the identified correction plane and at the proper rotational position.
The determination of unbalance in vehicle wheel rim and tire assemblies is carried out by an analysis of the phase and amplitude of the mechanical vibrations caused by the rotating unbalanced mass of the wheel rim and tire assembly. The mechanical vibrations are measured as motions, forces, or pressures by means of transducers, which convert the mechanical vibrations to electrical signals. The electrical signals are subsequently analyzed by a suitably programmed microprocessor. Each electrical signal is representative of a combination of fundamental oscillations caused by the rotating imbalance mass and noise.
It is well known in the art that a variety of types of imbalance correction weights are available for placing on a wheel rim to correct a measured imbalance. For example, adhesive-backed weights, patch balance weights, and hammer-on weights are available from a number of different manufacturers. Most wheel balancer systems are configured to assume that the wheel rim and tire assembly will be rotated to a particular rotational position (for example, disposing the desired weight correction position at the top—twelve o'clock—or bottom—six o'clock—rotational positions) during placement of an imbalance correction weight. This is generally not a problem, unless it would be more convenient to apply the weight with the wheel rim and tire assembly in a different rotational position, for example, the four or five o'clock rotational positions, when the operator is standing facing the surface of the wheel rim and tire assembly mounted on the wheel balancer system.
To compensate for a combination of static imbalance (where the heaviest part of the wheel rim and tire assembly will naturally tend towards a rotational position directly below the mounting shaft) and couple imbalance (where the rotating wheel rim and tire assembly exerts torsional vibrations on the mounting shaft), at least two correction weights are typically required to be separated axially along the wheel rim surface, coincident with weight location or imbalance correction “planes”. For imbalance correction weights of the “clip-on” style, the “left plane” comprises the left (innermost) rim lip circumference while the “right plane” comprises the right rim lip. If imbalance correction weights of the “adhesive” style are used, the imbalance correction planes can reside anywhere between the rim lips, barring physical obstruction such as wheel spokes, valve stems, welds, or regions of excessive wheel rim curvature.
With the wheel rim and tire assembly mounted to the wheel balancer system, a scan of the wheel rim inner surface profiles is optionally acquired, either with a mechanical contact system, such as is described in U.S. Pat. No. 6,484,574 B1 to Douglas et. al. or a non-contact measurement system, such as is described in U.S. Pat. No. 6,535,281 B2 to Conheady, et al.
Next, the imbalance correction planes are selected and the relative distances from a reference plane (usually the surface of the wheel mounting hub) to each of the imbalance correction planes is either conventionally measured either by manual measurement with a pull-out gauge or caliper, and manual input of the observed values through a keypad, potentiometer, or digital encoder, or by using an automatic electronic measuring apparatus which provides a direct measurement of the relative distance to the wheel balancer microprocessor. The radius of the wheel rim at which the weights will be placed must also be entered, again either manually, or by use of the electronic measuring apparatus.
Conventional wheel balancers can also employ a microprocessor configured to utilize the input weight plane information, together with variable weight amounts and variable radial placements, to identify proper locations for placement of the imbalance correction weights on the wheel rim, and to control rotation of the wheel rim and tire assembly. While utilization of such a balancer system facilitates the placement of an imbalance correction weight by placing the vehicle wheel rim and tire assembly in a preferred, or optimal rotational position for placement of the imbalance correction weight, it does not reduce other sources of operator error, such as the physical placement of an imbalance weight on the wheel, a poor selection of imbalance planes by the operator, or failure to compensate for the width of the imbalance weights during installation.
Automatic positioning of the wheel rim and tire assembly to a predetermined imbalance correction weight placement rotational position can be enhanced with the addition of a visual guide to the operator. U.S. Pat. No. 6,484,574 B1 to Douglas et al. combines a continuous laser projection guide with wheel balancer system including a direct current motor. The wheel balancer includes a shaft adapted for receiving a wheel rim and tire assembly, having a longitudinal axis and which is rotatable about the axis by a controllable motor, so as to rotate a wheel rim and tire assembly removably mounted thereon. A rotation sensor assembly is provided for measuring rotation of the shaft about its longitudinal axis and a vibration sensor assembly is operatively connected to the shaft for measuring vibrations resulting from imbalance in the wheel rim and tire assembly. A control circuit controls the application of power to the motor and determines from vibrations measured by the vibration sensor assembly, at least one weight placement position on the wheel rim and tire assembly to correct the vibrations. The control circuit is responsive to determination of an imbalance correction weight plane to project a laser projection onto the surface of the wheel rim at the selected imbalance correction plane. The controller then rotates the wheel rim and tire assembly to bring the weight placement position to a predetermined rotational location coinciding with the laser projection in the imbalance correction weight plane, and to actively hold the wheel rim and tire assembly in that rotational location at which an imbalance correction weight is to be placed.
During a wheel balancing procedure, an operator must divide attention between information and instructions displayed on the console of the wheel balancer system and the laser projection on the surface of the wheel rim for imbalance correction weight placement. Accordingly, it would be advantageous to provide a vehicle wheel rim and tire balancer system with the ability to project a two-dimensional display of visual information onto the surface of a vehicle wheel rim to assist an operator in completing a vehicle wheel rim and tire balancing procedure.
It would be further advantageous to utilize a projected two-dimensional display on the surface of a vehicle wheel rim and tire assembly to facilitate non-contact measurements of a vehicle wheel rim and tire assembly surface profile through the projection and observation of a series of points, lines, or patterns on the surface of the vehicle wheel rim and tire assembly.